About peak and loop in sludge rheograms

The thixotropic behavior of sewage sludge is analysed by varying several parameters such as the time of rest, the slope of the shear rate ramp or the data sampling. We observed that only the initial stress overshoot is time-dependent but always appears, for a given material, at the same critical angle which indicates it is linked to elastic effects: during shear, the material has a short memory. The visualisation of the velocity profile within the sheared material confirms this assumption. We also demonstrate that the hysteresis area is highly dependant on the data sampling and cannot be considered as a material characteristic. Finally, we pointed out that shear rate cycles are not the most powerful method to characterize thixotropy.     

泥石流阵性流和触变唯象模型的探讨

泥石流体的触变性可以较好地展示泥石流的阵性流和冲淤变化机理，泥石流触变滞后环（下降段）具有促进泥石流阵性流产生的作用。本文首次用实验方法探讨了泥石流浆体的触变唯象模型η＝η∞／ｔｃγ＋η∞。该触变模型展示了定态粘度（η）、剪切速率（γ）和滞后环模型参数关系，并与试验结果相吻合。它为泥石流防治提供了确切参数。